Such a line printer is provided with a plurality of printing type wheels, each of which has printing types at its periphery and can be stopped at the printing position, and a hammer, which is disposed so as to be opposed to the printing type wheels, and so constructed that desired printing types are transcribed on recording paper by the fact that the hammer pushes the recording paper, which is located so as to be opposed through an ink ribbon to the printing wheels or which is located so as to be opposed to the printing wheels, on which ink is applied by means of an ink roll, against printing types selected to be at the printing position.
However, for such a printer, it is necessary that the hammer described above has a superficial hardness greater than a certain value and at the same time that the hammer is deformable, in order to transcribe clearly the printing types on the recording paper. For the purpose of satisfying these requirements, heretofore, a hammer illustrated in FIG. 16 has been proposed.
In FIG. 16 the reference numeral 100 represents a printing type wheel having printing types 101 on its peripheral surface; 102 recording paper; and 103 a hammer. The hammer 103 consists of a holder 105, which is rotatable in the direction indicated by an arrow around a supporting shaft 104, a cylindrical body 106 made of an elastic material, such as rubber, etc., held at the extremity of this holder 105 and a sleeve 107 made of a relatively hard material, such as a synthetic resin, etc., which is fitted into this cylindrical body 106.
Now, when the hammer 103 is rotated up to the printing position, as indicated in FIG. 16, where the printing wheel 100 is stopped, so that a desired printing type 101 is located at the printing position and recording paper 102 is carried to the position opposite to the printing type 101, the cylindrical body 106 of the hammer 103 is compressed and deformed and its repulsive force acts through the hard sleeve 107 on the recording paper 102. In this way, the recording paper 102 is pushed against the printing type 101, which is at the printing position, by the thrusting force of the hammer and the desired type is transcribed on the recording paper 102.
However, in the prior art example described above, since the hammer 103 is constituted of the holder 105, the cylindrical body 106 and the sleeve 107, it has drawbacks that the construction is complicated and that the production cost rises and the number of steps for assembling is increased. Furthermore it is another drawback that, when the center of supporting shaft 104 or the cylindrical body 106 is deviated from the center of the printing type wheels 100, the thrusting force of the hammer 103 cannot act uniformly on the plurality of the printing type wheels and thus non-uniformity of the print is produced.
Further, in such a printer there is a drawback that, when the size of the printing wheel and the interval between two adjacent printing types are reduced for the purpose of reducing the size of the whole printer, printing types other than the selected printing types are brought into contact with the recording paper so that erroneous printing types are transcribed or the recording paper becomes dirty.